The phrase "new axles" refers to replacing the mechanical part that connects the wheels of a vehicle. It means getting rid of the old ones and installing brand new ones. Full definition
So, Advance Auto Parts did a defective replacement for me on the parts since that is where I initially purchased them and happy me left the mechanics with new axles just to start hearing that noise not 2 miles down the road with some very bizarre shaking and vibrating going on!!! (mechanics.stackexchange.com)
In the past few years, however, the trend pointed into the opposite direction: Increased demands for driving dynamics, safety, and comfort made car chassis constructions more and more complex and heavier — more structural components, new axle designs, integration of active suspension components. (greencarcongress.com)